Whole blood is made up of various cellular and non-cellular components such as red cells, white cells and platelets suspended in its liquid component, plasma. Whole blood can be separated into its constituent components (cellular, liquid or other), and the separated component can be administered to a patient in need of that particular component. For example, red blood cells may be separated from the whole blood of a healthy donor, collected, and later administered to a patient.
Commonly, more than one component of blood is prepared from a unit of whole blood. For instance, red blood cells, plasma and platelets may all be prepared from the same unit of whole blood. Protocols used to prepare blood components often involve the addition of an anticoagulant containing citrate such as, but not limited to, citrate phosphate dextrose (CPD) to the collected whole blood. However, the optimal protocol for the preparation and storage of one component may often differ from the protocol for the preparation and storage of another component. For instance, units of whole blood used to prepare platelets are typically stored at room temperature, approximately 20-24° C., often approximately 22° C., before processing, while storage at approximately 4° C. is optimal for the preparation of red blood cells.
At blood processing centers or similar locations, it is often convenient to accumulate a large number of units of whole blood before separating (i.e., processing) the blood components. The processing of multiple units of blood at one time, for example, in the morning of the day following collection reduces processing costs and also ensures uniformity of preparations. For example, staff for processing the blood may be required only during business hours (rather than requiring staff to work after business hours to process blood collected that same day) and a consistent routine may be readily developed. However, whole blood may be held for at least 8 hours and up to 26 hours before processing and separation of blood components when this procedure is followed.
While holding blood overnight provides logistical and staffing benefits to the blood center, the holding of blood for 8 or more hours is not without its drawbacks when it comes to preserving or maintaining the functionality of certain components, such as red blood cells. For example, compared to samples in which whole blood was held for only 8 hours or less at room temperature before the preparation of red blood cells, holding whole blood at room temperature overnight, which is at least 8 hours and may be up to 26 hours, generally is associated with the reduction of 2,3-DPG (2,3-diphosphoglycerate) to very low levels, an initial increase in ATP levels followed by a steady decline during storage at 4° C., and reduced levels of extracellular potassium when the cells are stored in a red cell storage solution. Even within the 8-hour range, rapid cooling of whole blood to room temperature is recommended if the hold temperature will be beyond 4 hours to avoid initial loss of 2,3-DPG. (Högman et al., Transfusion. 1999; 39(5):492-497). These effects of holding of whole blood before processing may be a consequence of an association between the rate of synthesis of 2,3-DPG and the intracellular pH of red blood cells where breakdown of 2,3-DPG is favored below pH 7.2. (Hess et al., Transfusion 2002; 42: 747-752.)
In addition, compared to storage at cooler temperatures, the increased metabolism of red blood cells stored at room temperature results in increased production of lactic acid (and also at temperatures above room temperature) resulting in a rapid fall to lower pH levels. While storage of whole blood at 4° C. and the consequent reduction of red blood cell metabolic rate may delay this effect, platelets, on the other hand, cannot be prepared from blood stored at 4° C.
Consequently, the preparation of red blood cells and platelets from the same unit of whole blood that has been held at room temperature until processing may impair the functionality of the red blood cells and reduce the time that the red blood cells may be stored. Therefore, it would be desirable to provide a storage solution that allows the long term storage of red blood cells prepared from whole blood that has been held at room temperature (20-24° C.) for extended periods of time before processing.